A careful study of collision induced bond-breaking reactions in carbon cage compounds revealed that a substantial fraction of the fragmenting ion received 9-15 eV of internal energy during the collision process. Collision-induced-decomposition (CID) reactions were found to be useful for structural analysis of di-2-ethylhexylphthalate metabolites. A new tandem quadrupole mass spectrometer system has been developed for MS/MS studies. Kinetic energy release studies suggest the presummed retro-Diels Alder process in 5, 6, 6a, 7, 12, 12a-hexahydrobenzo(a)anthracene and related compounds is step-wise.